A Terminal Gothic Investigation
On the evening of October 14th, the entire household staff of Blackmoor Hall reported hearing three distinct knocks on the library door. When opened, the room was empty save for an open book on the reading desk -- turned to a page that had been carefully excised from every other copy of the same volume.
Book identified as "Principia Obscura," 1847 first edition. Page 113 intact only in this copy.
The excised page contained not text but a cipher -- 47 lines of seemingly random characters arranged in a grid. Dr. Hargreaves, the household cryptographer, spent three sleepless nights before recognizing the pattern: each line was a different substitution cipher, and the key to each was hidden in the line that followed it.
Partial decryption: "THE DOOR IS NOT A DOOR / THE BOOK IS NOT A BOOK / WHAT KNOCKS THREE TIMES..."
The investigation remains open. Blackmoor Hall was sealed in 1923 and has not been entered since. The book, the cipher, and the answer to what knocked three times on the library door remain within -- waiting for someone willing to turn the handle.